The paper aims to clarify the effect on pulp properties of adding fibers from used fiberboards to standard fibers. Fibers from industrial HDF, from used fiberboards and their mixtures were tested using a laboratory Fiber Analyser. Data were obtained directly for both fiber length and fiber width. The pulp was tested using computer image analysis to calculate the area share of different fiber length and width classes. The results show that the largest changes in pulp fiber dimensions occur when the percentage of recovered fibers, RF, is between 15% and 30%. The results obtained show that a qualitative analysis of fiber can be a useful tool for assessing the potential properties of fiberboards, especially when new materials are used.
The paper proposes the production of a three-layer MDF instead one layer boards. Three-layer panels have been made from fibers of varying dimensions for the outer and the core layers. The outer layers were produced from standard fibers, while the core layer from longer and thicker fibers (of lower pulp freeness). In order to determine the optimal technological parameters in the production of three layer boards, the experimental plan was used in the study. Three factors at two levels were tested. Analysis of variance (ANOVA) was used to analyze the significance of factors. Regression coefficients and 3D contour plots were used to quantify the relationship between panel properties and test factors. Properties of obtained boards were tested according to the standard EN 622-5/2010. All selected factors within the examined range of settings had influence on MDF properties. It has been found that the best properties of the plates were 25x50x25 involving layers, the content of the glue in the outer layers of 10% and the core layer of 12% at the time of overheating of the mats 90s.